Organic fluoro-surfactants such as perfluorooctane sulfonic acid (hereinafter abbreviated as “PFOS”) and perfluorooctanoic acid (hereinafter abbreviated as “PFOA”) are used as auxiliaries for fluororesin production. These organic fluoro-surfactants should not be discharged to the environment because they are stable and less degradable substances. In addition, organic fluoro-surfactants should preferably be recovered and reused as much as possible because they are expensive.
Some studies have been conducted on adsorbents capable of removing PFOS in water. Activated carbon is reported to be an effective adsorbent for removal of PFOS in water. However, activated carbon has such a disadvantage as it is difficult to be reused and enormous energy is necessary when adsorbed PFOS is recovered. In addition, when activated carbon is used in practical liquid waste treatment, adsorption efficiency goes down because activated carbon also has a high ability to adsorb organic substances other than PFOS.
Patent Document 1 reports that a cyclodextrin polymer derived from cyclodextrin is used as an adsorbent to adsorb and remove organic fluoro-compounds in water. It is, however, difficult to recover the adsorbed organic fluoro-compounds quantitatively or to reuse the adsorbent. There is still a high demand for improvements.